Figure 4. Young MSC-EVs, but not aging MSC-EVs, promoted M2 phenotype of alveolar macrophages in vivo. Mice were divided into 4 groups: control, LPS, LPS + young MSC-EVs (100 μg), LPS + aging MSCs-EVs (100 μg). (A and B) Total cells in the BAL were harvested at 24 h after LPS treatment. Cells were then stained with PE-conjugated anti-mouse F4/80 antibody and APC anti-mouse CD206 antibody for phenotypical analysis via flow cytometry. Data are presented as mean ± SEM, n = 8–12. **p < 0.01, *** p < 0.001. (C) Total cells in the BAL were harvested to isolate alveolar macrophages at 24 h after LPS treatment. Arg-1 mRNA levels of alveolar macrophages were analyzed via qRT-PCR. Data are presented as mean ± SEM, n = 6. *p < 0.05, **p < 0.01, *** p < 0.001.